1. Technical Field
The present invention relates to an ink set, an ink jet recording method, a recorded matter recorded by the ink jet recording method, and an ink jet recording apparatus. In particular, the invention relates to an ink set, an ink jet recording method, a recorded matter recorded by the ink jet recording method, and an ink jet recording apparatus in which a printed surface having a metallic gloss of any color tone can be formed.
2. Related Art
Hitherto, in order to form a printed surface having a metallic gloss on a printed matter, a printing method using a printing ink containing a gold powder or a silver powder which is prepared from brass particles, aluminum particles, or the like as a pigment, a foil stamping printing method using a metal foil, a thermal transfer method using a metal foil, or the like has been employed.
However, as for a printed surface obtained by using a printing ink containing a gold powder or a silver powder, the average particle diameter of a metal powder used is large; in the range of 10 to 30 μm, and thus matte metallic gloss can be obtained but it is difficult to obtain specular gloss. Meanwhile, in the foil stamping printing method or the thermal transfer method in which a metal foil is used, an adhesive is applied to a printing medium, and a flat and smooth metal foil is pressed thereon, or a recording medium is brought into close contact with a metal foil and heated to thermally fusion-bond the metal foil to the recording medium. Therefore, relatively good gloss can be obtained, but a special apparatus is necessary. Furthermore, the number of steps in the production increases, and pressure or heat is applied during the production steps. Accordingly, the recording medium is limited to, for example, a recording medium that is resistant against heat and deformation.
Recently, a large number of applications of ink jet in printing have been developed. An application thereof is a metallic printing. For example, JP-A-2002-179960 discloses a technique in which a metal coating film is formed on the surfaces of spherical plastic particles, and an ink composition containing the resulting pigment is printed by ink jet printing. However, in order to obtain high metallic gloss, it is necessary that the spherical particles be deformed to be flat so that the surfaces of the spherical particles become smooth. According to this technique, it is necessary to perform a pressing treatment with a roller and a heat treatment at the same time. Accordingly, it is inevitable that an apparatus and a production process are complicated in this respect, and the recording medium is also limited.
Furthermore, JP-A-2003-292836 and JP-A-2003-306625 disclose techniques using an ink composition in which a colloid of a noble metal such as gold or silver is dispersed. However, when the particle diameter of such a noble metal colloid is decreased to several nanometers to several tens of nanometers so as to give a priority to dispersion stability, coloring due to plasmon absorption occurs and metallic gloss for an ink composition cannot be obtained. In such a case, metallic gloss can be obtained by drying a printed surface, and then performing a heat treatment at 150° C. or higher to fusion-bond colloidal particles. On the other hand, when the particle diameter is increased in order to give a priority to metallic gloss, dispersion stability decreases, and thus problems such as aggregation and precipitation inevitably occur. Consequently, the storage life of the ink composition significantly decreases. In addition, obviously, using a noble metal as a material significantly increases the cost of the ink composition, and such an ink composition is used only for a high-value added application, which is disadvantageous in terms of the cost.
Furthermore, regarding a known metallic ink composition, a metallic pigment is mixed with a colorant, and the mixture is used as an ink composition. In this method, the metallic pigment and the colorant are separated from each other during printing, or only the metallic pigment precipitates and aggregates during the storage of the ink composition. Such a problem may result in printing defects such as color loss in which only the colorant is absorbed in a recording medium and only the metallic pigment remains on a surface, and the formation of a non-uniform image having unevenness.
In addition, the method in which a metallic pigment is mixed with a colorant and the resulting mixture is used as an ink composition has a problem that the expression of a metallic color is limited. For example, it is very difficult to express silver using an ink composition prepared by adding a yellow pigment to a metallic pigment so as to express gold. Accordingly, a method in which an ink composition containing only a metallic pigment is combined with a chromatic color ink composition containing any colorant is more preferable because any metallic color can be efficiently expressed in a large number of combinations.